Microgels and process for their preparation

ABSTRACT

A process for preparing microgel(s) that uses a wide range of activatable prepolymers; in the process, a polymer composition of crosslinked component A and soluble components B and C is formed from mono-olefinic and multi-olefinic monomers in the presence of catalyst and initiator; the process comprises:  
     I) introducing mono-olefinic monomer, catalyst, and initiator into a reactor in the absence of multi-olefinic monomer and producing an activatable prepolymer, component B;  
     II) contacting the product of I) with multi-olefinic monomer to produce components A and C, optionally in the presence of additional initiator; also optionally in the presence of additional mono-olefinic monomer and initiator; the ratio of components A/(B+C) can be controlled by varying the mole ratio of Component B/ multi-olefinic monomer from 0.05/1 up to 5/1, by decreasing the mole ratio to increase the ratio of A/(B+C), and increasing the mole ratio to decrease the ratio of A/(B+C).

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for the preparation ofa microgel. The term microgel includes microgels and star polymers.

[0002] Microgels are macromolecules which possess a very high molecularweight and yet a low viscosity similar to linear or branched polymers ofrelatively low molecular weight. Microgels are an intermediate structurebetween conventional linear or branched polymers such as polyethylene orpolycarbonate and networks such as vulcanized natural rubber. Thedimensions of microgels are comparable with high molecular weight linearpolymers but their internal structure resembles a network.

[0003] The properties of microgels make them particularly useful in awide range of applications such as in additives, in advanced materialformulations for foams or fibers, in coating compositions, binders andredispersible latexes. Microgels can also be used to improve the ease ofprocessing and to improve the structural strength and dimensionalstability of the final products. A further potential use for microgelsis as additives for high impact polymers. Microgels embedded in a matrixof conventional linear polymer can act to stabilize the whole structureby distributing mechanical tension. Microgels are also useful inbiological systems and as pharmaceutical carriers.

[0004] Care is required in preparing microgels as the multiple doublebonds present within these systems can readily undergo intermolecularreactions which can lead to intractable networks. PCT/AU98/00015discloses a process for microgel preparation involving reacting analkoxyamine with a crosslinking agent. Procedures such as thosedescribed by Okay and Funke in Macromolecules, 1990, 23, 2623-2628,require high purity solvent and reagents as well as an inert atmosphereand are complicated by undesirable side reactions. Despite the uniqueproperties of microgels, the difficulties in preparing them have limitedtheir potential and commercial use.

SUMMARY OF THE INVENTION

[0005] This invention concerns a new process for preparing microgel(s)employing a wide range of activatable prepolymers. The process of thisinvention produces a polymer composition of crosslinked component A andsoluble components B and C from mono-olefinic and multi-olefinicmonomers in the presence of catalyst and initiator. The processcomprises:

[0006] I) introducing mono-olefinic monomer, catalyst, and initiatorinto a reactor in the absence of multi-olefinic monomer and producing anactivatable prepolymer component B;

[0007] II) contacting the product of I) with multi-olefinic monomer toproduce components A and C, optionally in the presence of additionalinitiator, also optionally in the presence of additional mono-olefinicmonomer and initiator. The ratio of components A/(B+C) can be controlledby varying the mole ratio of (Component B)/(multi-olefinic monomer) from0.05/1 up to 5/1, by decreasing said mole ratio to increase the ratio ofA/(B+C), and increasing said mole ratio to decrease the ratio ofA/(B+C).

[0008] Component B is the soluble species made in step I, A is theinsoluble species made in Step II and C is the soluble species made inStep II.

[0009] The prepolymer, B, will be comprised of an activatableprepolymer. As will be understood by one skilled in the art having thisdisclosure as guidance, the activatable prepolymer is a polymer thatunder the conditions of the experiment can reversibly generatepropagating radicals. The activatable prepolymer contains a group whichis adapted to reversibly cleave from the prepolymer B under activatingconditions to provide a reactive propagating radical and so promoteliving/controlled polymerization.

[0010] The term activatable prepolymer includes a polymer containingactivated halogen (or pseudohalogen) groups, a polymer terminated withthiocarbonylthio groups (including dithiocarbamate, dithiocarbonate,trithiocarbonate, dithioester groups), a macromonomer (a polymer chainhaving at least one polymerizably-active functionality per polymerchain).

[0011] Methods for Preparing Component B(Step I)

[0012] Polymers containing halogen (or pseudohalogen) groups areactivatable prepolymers in atom transfer radical polymerization (ATRP).Typical examples of transition metal catalysts for atom transfer radicalpolymerization include complexes such as CuX/2,2′-bipyridyl derivatives,CuX/Schiff base complexes, CuX/N-alkyl-2-pyridylmethanimine,CuX/tris[2-(dimethylamino)ethyl]amine,CuX/N,N,N′,N″,N″-pentamethyldiethylenetriamine,CuX/tris[(2-pyridyl)methyl]amine, Mn(CO)₆, RuX_(x)(PPh₃)₃,NiX{(O—O′—CH₂NMe₂)₂C₆H₃}, RhX(PPh₃)₃, NiX₂(PPh₃)₂ and FeX₂/P(n—Bu)₃wherein X is halogen or pseudohalogen and preferably chlorine orbromine. An alumoxane Al(OR)₃ may be used as a cocatalyst. It isbelieved that the mechanism of ATRP is described in the followingscheme:

[0013] Initially, the transition metal catalyst, M_(t) ^(n), abstractsthe halogen atom X from the initiator, an arene or alkane sulfonylhalide, R—X, to form the oxidized species, M_(t) ^(n+1)X, and the sulfurcentered radical R. In the subsequent step, the radical, R., reacts withunsaturated monomer, M, with the formation of the intermediate radicalspecies, R—M. The reaction between M_(t) ^(n+1)X and R—M. results in theproduct, R—M—X, and regenerates the reduced transition metal species,M_(t) ^(n), which further reacts with R—X and promotes a new redoxcycle. When polymeric halides, R—M_(n)—X, are reactive enough towardM_(t) ^(n) and monomer is in excess, a number of atom transfer radicalevents, i.e., a living/controlled radical polymerization occurs.Further, details of this mechanism are described in the reference:Macromolecules, 1995, 28, 7901. See also Macromolecules, 1995,28,7970and Macromolecules, 1996,29,3665 concerning living/controlled radicalpolymerization using a combination of an arenesulfonyl chloride oralkane sulfonyl chloride and a transition metal compound.

[0014] One part of the polymerization system in the process is anarenesulfonyl halide or an alkanesulfonyl halide of the Formula A¹SO₂Xwherein A¹ is an aryl, substituted aryl group, an alkyl group or asubstituted alkyl group, and X is chlorine, bromine or iodine. Includedwithin the meaning of arenesulfonyl halide and alkanesulfonyl halide isany adduct, such as a 1:1 adduct, which is a reaction product of anarene- or alkyl-sulfonyl halide and any polymerizable vinyl monomer. Ineffect, such an adduct is one of the initial products in thepolymerization process itself.

[0015] Another component of the polymerization process system is acompound containing a lower valent transition metal atom. By this ismeant a compound containing at least one transition metal atom that iscapable of existing in a higher valent state. Included within thedefinition of a compound containing a transition metal atom in a lowervalent state is a compound or combination of compounds that under thepolymerization process conditions can form in situ the desired compoundcontaining a transition metal atom in a lower valent state. In somecases, this can include metal itself (or an alloy or a metal oxidethereof) which can dissolve and/or be solubilized to some extent in theprocess medium.

[0016] Suitable lower valent metals include Cu[I], Ru[I], Ni[II],Re[II], Pd[II], Cu[0], Ni[0], Fe[0], Pd[0], and Rh[II]. The transitionmetal compound should preferably be at least slightly soluble in thepolymerization medium. Optionally, the transition metal compound whichis added can be solublized by the addition of a complexing agent such asa 2,2′-bipyridine derivative, for example,4,4′-di(5-nonyl)-2,2′-bipyridine. The complexing agent should also bechosen such that the transition metal has the appropriate redoxpotential. Other suitable complexes are listed above. The molar ratio oflower valent transition metal compound:arenesulfonyl halide oralkanesulfonyl halide is not critical, but it is preferred that it begreater than 0.2, more preferably greater than 0.5, especially if aliving polymerization is desired. It is also preferred that this rationot be over 5, and more preferably be less than 2.

[0017] Thiocarbonylthio and related transfer agents and reactionconditions for the use of these compounds in producing activatableprepolymers are disclosed in Int. Patent Applications WO 98/01478, WO99/05099 and WO 99/31144 which are incorporated herein by reference.

[0018] Preferred thiocarbonylthio chain transfer agents used to form theactivatable prepolymer are represented by Formulas III a-c.

[0019] In Formula IIIa:

[0020] Z is selected from the group consisting of hydrogen, chlorine,optionally substituted alkyl, optionally substituted aryl, optionallysubstituted heterocyclic ring, optionally substituted alkylthio,optionally substituted arylthio, optionally substituted alkoxy,optionally substituted aryloxy, optionally substituted amino, optionallysubstituted alkoxycarbonyl, optionally substituted aryloxycarbonyl,carboxy, optionally substituted acyloxy, optionally substitutedaroyloxy, optionally substituted carbamoyl, cyano, dialkyl- ordiaryl-phosphonato, dialkyl-phosphinato or diaryl-phosphinato and apolymer chain.

[0021] R⁷ is selected from the group consisting of optionallysubstituted alkyl, optionally substituted alkenyl, optionallysubstituted alkynyl, optionally substituted (saturated, unsaturated oraromatic) carbocyclic ring, optionally substituted (saturated,unsaturated or aromatic) heterocylic ring, optionally substitutedalkylthio group, and a polymer chain. R⁷ is chosen such that it forms afree radical leaving group that can initiate free radical polymerizationunder the reaction conditions.

[0022] In Formula IIIb:

[0023] n is an integer greater than 1; R^(7′) is an n-valent moietyderived from R⁷ as defined in Formula IIIa and Z is as defined forFormula IIIa.

[0024] In Formula IIIc:

[0025] n is an integer greater than 1; R⁷ is as defined in Formula IIIa;and Z′ is an n valent moiety derived from a species selected from thegroup consisting of optionally substituted alkyl, optionally substitutedaryl and a polymer chain where the connecting moieties are selected fromthe group consisting of aliphatic carbon, aromatic carbon, oxygen andsulfur.

[0026] The substituents for the substituted moieties referred to abovefor R⁷, R^(7′), Z and Z′ are selected from the group consisting ofhydroxy, tertiary amino, halogen, cyano, epoxy, carboxylic acid, alkoxy,alkyl having 1-32 carbon atoms, aryl, alkenyl having 2-32 carbon atoms,alkynyl having from 2-32 carbon atoms, saturated carbocyclic ringshaving 3-14 carbon atoms, unsaturated carbocyclic rings having 4-14carbon atoms, aromatic carbocyclic rings having 6-14 carbon atoms,saturated heterocyclic rings having 3-14 carbon atoms, unsaturatedheterocyclic rings having 4-14 carbon atoms aromatic carbocyclic ringshaving 4-14 carbon atoms.

[0027] By a “polymer chain” referred to above for R⁷, R^(7′), Z and Z′is meant conventional condensation polymers, such as polyesters [forexample, polycaprolactone, poly(ethylene terephthalate), poly(lacticacid)], polycarbonates, poly(alkylene oxide)s [for example,poly(ethylene oxide), poly(tetramethylene oxide)], nylons,polyurethanes, or chain polymers such as those formed by coordinationpolymerization (for example polyethylene, polypropylene), radicalpolymerization (for example, poly(meth)acrylates and polystyrenics),anionic polymerization (for example, polystyrene, polybutadiene),cationic polymerization (for example, polyisobutylene) and grouptransfer polymerization (for example, poly(meth)acrylates).

[0028] Other multifunctional thiocarbonylthio compounds also can beused.

[0029] Another class of polymer component B comprises macromonomersdepicted by Formula IV and include those disclosed in Int Pat Appl.WO96/15157 and U.S. Pat. No. 5,264,530. Reaction conditions for the useof these compounds in producing activatable prepolymers are alsodisclosed. Preferably macromonomers contain a maximum of 2 double bonds,more preferably macromonomers contain 1 double bond per polymer chain:

[0030] Macromonomers of this type can be prepared by a number ofdifferent methods. Two illustrative methods of preparation are (1) useof catalytic chain transfer agents containing Co^((II)) or Co^((III));and (2) addition-fragmentation polymerization. These methods arediscussed by Rizzardo et al. in Macromol. Symp. 1997, 111,1.

[0031] X is selected from the group consisting of halogen, optionallysubstituted aryl, alkoxycarbonyl, optionally substitutedaryloxycarbonyl, carboxy, optionally substituted acyloxy, aroyloxy,optionally substituted carbamoyl, and cyano.

[0032] P is a oligomer or polymer chain as defined above. P is chosensuch that it forms a free radical leaving group that can initiate freeradical polymerization under the reaction conditions.

[0033] The prepolymer component B comprises one or more monomer units;however, it is particularly preferred that the prepolymer is an oligomercomprising at least 3 monomer units and more preferably at least 5monomer units. The molecular weight (weight average) of the prepolymercomponents is preferably at least 1000 and more preferably from about3,000 to 25,000.

[0034] Step II: Preparation of Microgel

[0035] When the prepolymer includes at least three monomer units(preferably at least 5), the resulting microgel takes the form of lineararms of prepolymer linked to a crosslinked network forming a core. Thistype of microgel can conveniently be referred to as a star microgel.

[0036] The proportion of components used in the process of the inventionwill generally depend on the desired properties of the microgel and theintended application. Generally, the microgel is prepared using up to 60mole percent of crosslinking agent based on moles of polymerizablecomponents. More preferably, the crosslinking agent will comprise up to50 mole percent of the total of the polymerizable components. Typically,the prepolymer component B will compose from about 0.1 to 95 molepercent of the polymerizable components.

[0037] The present invention allows a higher proportion of crosslinkingagent than has previously been possible for microgel compositions. Priorart microgels have generally been restricted to using no more thanseveral mole percent of crosslinking agent. The ability to use highconcentrations of crosslinking agent enables microgels to be preparedwith a high density conferring significant advantages in rheologycontrol. Accordingly, it is preferred that the process of the inventionuses at least 0.5 mole percent of crosslinking agent based on total ofthe polymerizable components and most preferably from 0.5 to 50%.

[0038] In the process of the present invention, when the average numberof monomeric units in the prepolymer portion of the adduct is less than5 monomeric units it is particularly preferred that the monomercomposition include additional monomer(s) selected from monounsaturatedmonomers and conjugated diene monomers. As the average number of monomerunits in the prepolymer portion of the adduct decreases, the improvementprovided by using monomer becomes more significant. When the number ofmonomeric units in the prepolymer is from 1 to 3, a monounsaturatedmonomer is typically used.

[0039] Typically, the unsaturated monomer is present in up to 80 molepercent based on the total number of moles of the polymerizablecomponents and more preferably from 10 to 80%.

[0040] When the number of monomer units present in the prepolymer isless than 5, the adduct is preferably present in an amount of from 5 to60 mole percent.

[0041] Star microgels are preferably prepared using from 50 to 95 molepercent of adduct and up to 45 mole percent of monounsaturated monomer.

[0042] The additional monomer(s) used in the process of the inventioncan be any monounsaturated monomer such as an alkene, acrylate,methacrylate, styrene, an alkylstyrene (for example, vinyltoluene),other styrenic monomers, acrylonitrile, methacrylonitrile, vinylacetate, vinyl chloride or vinylidene chloride, or a conjugated dienemonomer such as butadiene, isoprene, chloroprene, or cyclopentadiene.

[0043] The properties of the microgel and its reactivity in subsequentapplications is controlled by the choice of monomers and theirfunctional groups. Examples of monomers include C₂ to C₁₀ alkenes, alkylacrylates, alkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkylmethacrylates, haloalkyl acrylates, haloalkyl methacrylates, alkoxyalkylacrylates, alkoxyalkyl methacrylates, N-substituted or N,N-disubstitutedaminoalkyl methacrylates, cycloalkyl acrylates, cycloalkylmethacrylates, phenyl acrylate, phenyl methacrylate, alkylene glycolacrylate, alkylene glycol methacrylate, poly(alkylene glycol) acrylate,poly(alkyleneglycol) methacrylate, acrylamides, methacrylamides,derivatives of acrylamindes and methacrylamides, esters of fumaric acid,maleic acid, maleic acid anhydride, N-vinylcarbazole,N-vinylpyrrolidone, vinylpyridine, benzyl acrylate and benzylmethacrylate.

[0044] When the prepolymer is an oligomer, the oligomer can be ahomopolymer or a copolymer. When the oligomer is a copolymer, it can bea statistical, an alternating, a gradient, or a block copolymer. Themonomers used in preparing the oligomer can include one or morefunctional groups in addition to the double bond. These additionalfunctional groups are selected to confer the desired polarity orreactivity on the arms of the star type microgel. Examples of additionalfunctional groups include halo, amino, hydroxy, carboxyl, mercapto,substituted amino, silane groups and epoxy. Hydroxyfunctional groupssuch as in the monomer hydroxyethyl methacrylate are particularlypreferred. A monomer which includes the additional functional group orgroups can be incorporated as a homopolymer chain or as part of astatistical or block copolymer.

[0045] Statistical or gradient copolymers can be prepared by using amixture of monomers. Block copolymers can be prepared by introducingmonomers sequentially to provide a block of the first monomer before thesecond is introduced.

[0046] The multiolefinic compound used in the process of the inventionpreferably contains two or more carbon-carbon double bonds. Otherfunctional groups such as hydroxyl, carboxyl, ester, amide, amino,substituted amino, mercapto, silane and epoxy or the like can be presentif desired. Examples of suitable multi-olefinic compounds includedivinylbenzene and derivatives of divinylbenzene and monomers containingtwo or more acrylate or methacrylate functional groups. Examples of suchpolyacrylate compounds include polyols substituted with two or moredouble bonds derived from acrylic or methacrylic acids.

[0047] Examples of di- and tri-acrylate compounds include compounds ofFormula XI:

[0048] wherein R⁸ and R⁹ are independently selected from hydrogen,halogen, C₁ to C₆ alkyl, preferably methyl, and substituted C₁ to C₆alkyl such as C₁ to C₆ hydroxyalkyl;

[0049] Y¹ and Y² are independently selected from NR¹⁰ and O where R¹⁰ isindependently selected from hydrogen and alkyl (preferably methyl)substituted C₁ to C₆ alkyl (such as C₁ to C₆ hydroxyalkyl) aryl, andsubstituted aryl; and

[0050] Q is any linking group known in the art. Preferred linking groupsinclude alkylene (preferably of 1 to 12 carbon atoms), a carbocyclic orheterocyclic group, a polyalkylene oxide, polyester or polyurethanechain and wherein the groups can optionally be substituted with one ormore substituents selected from halo, hydroxy, tertiary amino,substituted amino, silane, epoxy. Q can also contain acrylate ormethacrylate group.

[0051] Preferably, Q is alkylene of 1 to 10 carbon atoms or apoly(alkylene oxide) and optionally include a substituent selected fromhydroxy, amino, silane, epoxy and acrylate or methacrylate. When one orboth of R⁸ and R⁹ are substituted alkyl, suitable substituents includehydroxy, halo, amino, substituted amino, thiol, silane and epoxy.

[0052] Preferred polyacrylate compounds include trimethylolpropanetriacrylate, trimethylol propane trimethacrylate, pentaerythritoltetraacrylate, pentaerythritol tetramethacrylate, pentaerythritoltriacrylate, pentaerythritol trimethacrylate, alkylene glycoldiacrylates, alkylene glycol dimethacrylates, poly(alkyleneglycol)dimethacrylates, poly(alkylene glycol)diacrylates,poly(oxyalkylene glycol)dimethacrylates, poly(oxyalkyleneglycol)diacrylates, 2-cyanoethyl acrylate, alkylene glycol acrylate ormethacrylate, poly(alkylene glycol)acrylate or methacrylate. Specificexample of multi-olefinic compounds include divinylbenzene, ethyleneglycol dimethacrylate, butanediol dimethacrylate, triethylene glycoldiacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate,triethylene glycol diacrylate, pentaerythritol triacrylate, 1,3-butyleneglycol diacrylate and ethylene glycol acrylate methacrylate and otherpolyol acrylates or methacrylates.

[0053] Allyl and substituted allyl derivatives, such as esters ofacrylic and methacrylic acid, ethers and amines can also be used asmulti-olefinic compounds. Some examples are listed below:

[0054] Other unsubstituted compounds:

[0055] where n=0-4

[0056] The crosslinking agent can be used to control the architectureand chemical properties of the crosslinked network which constitutes thecore of the star microgel. Three general types of multi-olefiniccompounds can be used depending on the properties required.

[0057] When the unsaturated groups in the crosslinking monomer areequivalent, their relative reactivity is determined by statisticalconsiderations. A greater degree of control is provided when theunsaturated groups have different reactivities. Without wishing to bebound by theory, we believe the greater control provided by usingunsaturated group(s) of different reactivities occurs due to theoccurrence of chain growth at one of the double bonds prior tocompletion of crosslinking. The other type of crosslinking agent whichcan be used includes additional functional groups selected to providethe desired interaction with solvents or other species or the reactivityof the microgen. These three groups of crosslinkers will be discussed inmore detail.

[0058] Examples of multi-olefinic compounds in which the vinyl groupsare of equivalent reactivity include divinyl benzene and compounds ofFormula XI wherein R⁸ and R⁹ are similar, Y¹ and Y² are similar, and Qis unsubstituted or has symmetrical substitution. Commercially availablemonomers of this type include alkylene glycol diacrylates anddimethacrylates such as 1,4-butanediol diacrylate or 1,4-butanedioldimethacrylate.

[0059] Examples of multi-olefinic compounds in which the vinyl groupshave different reactivities include compounds wherein R⁸ and R⁹ aredifferent and/or Y¹ and Y² are different. Such multi-olefinic compoundscontain two different unsaturated groups selected from acrylate,methacrylate, acrylamide and methacrylamide. The two different saturatedgroups can be linked for example by alkylene glycol or polyalkyleneglycol linking groups.

[0060] Particularly preferred multi-olefinic compound with distinctvinyl groups include the following:

[0061] R=(CH₂)_(n) or (CH₂—CH₂—O—)_(n)CH₂—CH₂—

[0062] R¹, R² independently selected from H and alkyl

[0063] Another group of multi-olefinic compounds which are useful in theinvention are compounds which in addition to at least two unsaturatedgroups further include one or more other functional groups such ashydroxyl, mercapto, amine, halo, amido and alkoxycarbonyl. Substitutedcompounds of this general type are particularly useful in producing starmicrogels having a hydrophilic core or a core including reactive groups.Specific examples of such multi-olefinic compounds includehydroxy-substituted compounds such as pentaerythritol triacrylate andcompounds of Formula XI wherein Q includes one or more substituentsselected from hydroxyl, amino, substituted amino, silane, and epoxy or agroup of structure XII.

[0064] The process of this invention can use a mixture of multi-olefiniccompounds. For example, the use of multi-olefinic compounds fromdifferent classes such as divinyl benzene and diacrylates ordimethacrylates can provide advantages. Further, combinations ofsymmetrical multi-olefinic compounds and multi-olefinic compounds havingdouble bonds of different reactivities can be used to controlcrosslinking density.

[0065] The process of the invention can be conducted in the presence ofa solvent, if desired, and can be conducted in solution, in bulk or insuspension.

[0066] In preparation of star microgels, the reaction is preferablyconducted in a suitable solvent for the oligomer and theta-solvents areparticularly preferred. In some cases, the crosslinking reaction ishighly efficient when a mixture of crosslinking agent and a monomercontaining one unsaturated group is employed and it is believed themonomer acts as a spacing unit. It is also preferred that the spacingmonomer solvate the arms of the star-type microgel which are derivedfrom the oligomer.

[0067] Without wishing to be bound by theory, we believe the monomerdiluent acts as a spacer monomer to control crosslinking density and toimprove the efficiency of crosslinking. In some systems, it can bedifficult to obtain efficient crosslinking and microgel formation in theabsence of a suitable monomer such as monounsaturated monomer.

[0068] The spacer monomer can comprise a monomer having one or moreadditional functional groups to provide a means for controlling thereactivity or chemical properties of the microgel. For example, in oneembodiment, the spacer monomer comprises at least two types of monomersincluding a monomer which provides a relatively inert monomer unit and afunctionalized monomer incorporating one or more additional functionalgroups such as hydroxyl, carboxyl, amides, amino substituted amino,thiol, silane, epoxy or the like.

[0069] The spacer monomer can be the same or different from the monomerused in preparing the oligomer. However, in many cases it is convenientto use the same monomer. The spacer monomer is typically in the range offrom 0 to 99 mole percent of the polymerizable components.

[0070] The process of the present invention generally has thesignificant advantage over prior art processes in that it allowsoligomer arms to be incorporated much more efficiently so that theproportion of unreacted residual monomer in the resulting microgel isreduced.

[0071] The microgel prepared in accordance with the process of theinvention generally has a weight average molecular weight of at leastabout 10⁴. Preferably, the molecular weight is in the range of about 10⁴to 10⁸ and most preferably about 10⁵ to 10⁸. The molecular weight isdetermined by light scattering.

[0072] The microgels prepared according to the process of the inventionhave a range of applications as rheology control agents in solvent-borneand waterborne coatings and in adhesives and cosmetics.

[0073] In formulating a coating composition, it is desirable to providemaximum solids content and good durability. Whereas high solids contentis best satisfied by using a low molecular weight polymer, durability isbest satisfied by high molecular weight. The microgels of the presentinvention provide a polymer of high molecular weight, and hence gooddurability, while at the same time providing the solubility and flowproperties to enable a high solids content to be achieved. The microgelsalso allow a reduction in solvent content to be achieved without theproblems of sagging which occur with lower molecular weight resins.

[0074] The microgels of the invention can be used in thermosetting orradiation-curable compositions. Such compositions will generallycomprise a microgel which comprises pendant functional groups which canbe provided by using a monomer or a crosslinking agent which has theappropriate functional group such as a hydroxy, amino, carboxyl,mercapto, substituted amino, silane, carbamate or epoxy group. Thecrosslinking agent will contain functional groups which are reactivewith the pendant functional group of the microgen under the curingconditions.

[0075] The microgels are also useful as plastic additives to improveimpact resistance and internal lubrication and as a pharmaceuticalcarrier, particularly when prepared using polar functional groups, whichcan facilitate association of the microgel with the pharmaceutical.

EXAMPLE 1

[0076] A. Arm Formation via Dithioester Route

[0077] Isobutyl methacrylate (500 g, 2.52 moles), 2-ethylhexylmethacrylate (400 g, 2.82 moles), hydroxyethyl methacrylate (100 g, 0.77mole), 2-phenylprop-2-yl dithiobenzoate (27.7g, 0.10 mole), and toluene(450 g) were added to a three-necked 2 liter round bottom flask equippedwith a mechanical stirrer, condenser, heating mantle, and nitrogen purgeline. The solution was degassed with nitrogen for 20 minutes and thenheated to 110-115 C. When the reaction mixture had stabilized at 110-115C., Vazo®88 (7.5 g, 31 mmole) was added as a shot. The resulting mixturewas held at 110-115 C. for 6 hours.

[0078] B. NAD Formation Using Dithioester Arm

[0079] Dithioester arm (542 g) prepared above was added to a 3 literround bottom flask equipped as above along with: hydroxyethyl acrylate(56 g), methyl methacrylate (258 g), methyl acrylate (177 g), styrene(96 g), allyl methacrylate (32 g), heptane (483 g) and mineral spirits(128 g). This mixture was degassed with nitrogen for 15 minutes and thenheated to reflux. A mixture of Vazo®67 (11 g), mineral spirits (87 g),and butanol (41 g) was prepared and added to the reaction vessel over a210 minute period. After completion of this add, the reaction mixturewas held at reflux for 45 minutes. After the hold period, a mixture ofVazo®67 (6 g), and butanol (42 g) was added to the reaction vessel over90 minutes. After completion of this add, the reaction mixture was heldat reflux for 60 minutes and then 185 g of solvent were removed bydistillation at atmospheric pressure.

EXAMPLE 2

[0080] A. Preparation of Hydroxy Functional Macromonomer

[0081] To a 5-liter round bottom flask equipped with a mechanicalstirrer, thermometer, condenser, and heating mantle was added 545 gms ofisobutylmethacrylate(IBMA), 583.7 gms of 2-ethylhexylmethacrylate(EHMA), 95.6 gms of hydroxyethyl methacrylate(HEMA) and939.4 gms of toluene. This mixture was agitated and heated to refluxunder nitrogen. While maintaining the batch at reflux, a mixture of 1.1gms Vazo®88(1,1-azobis(cyanocyclohexane)), 31.7 gmns of HEMA, 60.1 gmsof toluene, and 32 mg of diaquobis(boron difluorodimethylglyoximato)cobaltate was added over a 10 minute period. This was followed by theaddition of a mixture of 388.6 gms IBMA, 561.4 gms EHMA, 103.6 gms HEMA,179.9 gms toluene and 4.0 gms Vazo®88 to the batch over 240 minuteswhile maintaining reflux. The batch was then held at reflux for 30minutes followed by the addition of a solution of 1.0 gm Vazo®88 in135.7 gms toluene over 60 minutes maintaining reflux. The batch was heldat reflux for 60 minutes and then colled to room temperature.

[0082] NAD Preparation With the Hydroxy Macromonomer

[0083] To a 3-liter round bottom flask equipped with a mechanicalstirrer, thermometer, condenser, and heating mantle 753.2 gms of theabove prepared macromonomer solution, 189.1 gms mineral spirits, and934.8 gms heptane were added. The solution was degassed with nitrogenfor 15 minutes and then heated to reflux. At reflux 1.8 gms of Vazo®67was added as a shot followed by the addition of a mixture of 109 gmshydroxyethyl acrylate, 500 gms methyl methacrylate, 342.8 gms methylacrylate, 185.6 gms styrene, 62 gms allyl methacrylate, 378.2 gms of theabove prepared macromonomer, 18.6 gms Vazo®67, 226.1 gms mineralspirits, 32.6 gms heptane, and 32.6 gms butanol over a 210 minute periodwhile maintaining reflux. Following a 45 minute hold period at reflux, amixture of 12.1 gms Vazo®67, 73.4 gms butanol, and 21.6 gms heptane wasadded over 90 minutes. The reaction mixture was then held at reflux foran additional 60 minutes and then 355.7 gms of solvent were removed bydistillation at atmospheric pressure.

EXAMPLE 3

[0084] Polymerization of Styrene via ATRP

[0085] Twenty milliliters of styrene(0.175 mole), 180 mgp-methoxybenzenesulfonyl chloride (8.71×10⁻⁴ mole), 30 mg of CuCl(3.03×10⁻⁴ mole) and 250 mg 4,4′-di-n-nonyl-2,2′-bipyridine (6.13×10⁻⁴mole) were added to a 250 ml Schlenk flask, and the solution wasdegassed by 4 freeze-pump-thaw cycles, and then the tube was filled withargon and heated at 120 C. for 17 hours. The polymerization was stoppedand the viscous solution was analyzed by NMR(conversion to polymer was67%) and GPC(Mn=1 5,400, Mw/Mn=1.29, based on a PS standard).Theoretical Mn assuming a living polymerization was 14,000. Thepolystyrene was isolated by precipitation of a THF solution in methanol,filtration and drying under vacuum.

[0086] B. NAD Formation Using Polystyrene Arm

[0087] Polystyrene arm (5.42 g) prepared above was added to a 500milliliter round bottom flask equipped with a mechanical stirrer,condenser, and thermometer along with: hydroxyethyl acrylate (0.56 g),methyl methacrylate (2.58 g), methyl acrylate (1.77 g), styrene (0.96g), allyl methacrylate (0.32 g), heptane (4.83 g) and mineral spirits(1.28 g). This mixture was degassed with nitrogen for 15 minutes andthen heated to reflux. A mixture of Vazo®67 (0.11 g), mineral spirits(0.87 g), and butanol (0.41 g) was prepared and added to the reactionvessel over a 210 minute period. After completion of this addition, thereaction mixture was held at reflux for 45 minutes. After the holdperiod, a mixture of Vazo®67 (0.06 g), and butanol (0.42 g) was added tothe reaction vessel over 90 minutes. After completion of this addition,the reaction mixture was held at reflux for 60 minutes.

We claim:
 1. A process for forming a microgel which comprise a core ofcrosslinked polymer and multiplicity of substantially linear polymericarms attached to the core said process wherein the process comprises: I)introducing mono-olefinic monomer, catalyst, and initiator into areactor in the absence of multi-olefinic monomer and producing anactivatable prepolymer component B which has a weight average molecularweight of 1,000-25,000; II) contacting the product of I) withmulti-olefinic monomer to produce components A and C, optionally in thepresence of additional initiator, also optionally in the presence ofadditional mono-olefinic monomer and initiator; wherein the ratio ofcomponents A/(B+C) can be controlled by varying the mole ratio of(Component B)/(multi-olefinic monomer) from 0.05/1 up to 5/1, bydecreasing said mole ratio to increase the ratio of A/(B+C), andincreasing said mole ratio to decrease the ratio of A/(B+C) the microgelhaving a weight average molecular weight of 10⁴-10⁸.
 2. A process forforming a microgel which comprise a core of crosslinked polymer andmultiplicity of substantially linear polymeric arms attached to thecore; wherein the process comprises (a) polymerizing monoethylenicallyunsaturated monomers in the presence of a thiocarbonylthio chaintransfer agent to form a prepolymer containing a thiocarbonylthio groupthat has a weight average molecular weight of 1,000-25,000; (b)polymerizing said prepolymer with monoethylenically unsaturated monomersand with 0.5-60 mole percent, based on the total moles of monomer of thecore, of multi-olefinic polymerizable monomers containing two or morecarbon-carbon double bonds which are crosslinked in the core to form themicrogel having a weight average molecular weight of 10⁴-10⁸; whereinthe monoethylenically unsaturated monomers of the core and theprepolymer are individually selected from the group consisting ofalkenes having 2-10 carbon atoms, alkyl (meth)acrylates having 1-12carbon atoms in the alkyl group, hydroxyalkyl (meth)acrylate, whereinthe alkyl groups have 1-4 carbons atoms, styrene, alkylstyrene,acrylonitrile, glycidyl (meth)acrylate, isobomyl (meth)acrylate,alpha-beta ethylenically unsaturated monocarboxylic acids, haloalkyl(meth)acrylates, alkoxyalkyl (meth)acrylates, aminoalkyl(meth)acrylates, N-substituted aminoalkyl(meth)acrylates,N,N-di-substituted aminoalkyl (meth)acrylates, cycloalkyl(meth)acrylates, phenyl (meth)acrylate, alkylene glycol (meth)acrylate,poly(alkylene glycol) (meth)acrylate, acrylamides, methacrylamides,esters of fumaric acid, esters of maleic acid, maleic acid, maleic acidanhydride, N-vinylcarbazole, N-vinylpyrrolidone, vinylpyridine, benzyl(meth)acrylate, vinyl acetate, vinyl chloride, vinylidene chloride,butadiene, isoprene, chloroprene and any mixtures thereof; and whereinthe thiocarbonylthio transfer agent is selected from the groupconsisting of

In Formula IIIa; Z is selected from the group consisting of hydrogen,chlorine, optionally substituted alkyl, optionally substituted aryl,optionally substituted heterocyclic ring, optionally substitutedalkylthio, optionally substituted arylthio, optionally substitutedalkoxy, optionally substituted aryloxy, optionally substituted amino,optionally substituted alkoxycarbonyl, optionally substitutedaryloxycarbonyl, carboxy, optionally substituted acyloxy, optionallysubstituted aroyloxy, optionally substituted carbamoyl, cyano, dialkyl-or diaryl-phosphonato, dialkyl-phosphinato or diaryl-phosphinato and apolymer chain; R⁷ is selected from the group consisting of optionallysubstituted alkyl, optionally substituted alkenyl, optionallysubstituted alkynyl, optionally substituted (saturated, unsaturated oraromatic) carbocyclic ring, optionally substituted (saturated,unsaturated or aromatic) heterocylic ring, optionally substitutedalkylthio group, and a polymer chain. R⁷ is chosen such that it formsfree radical leaving group that can initiate free radical polymerizationunder the reaction conditions; In Formula IIIb: n is an integer greaterthan 1; R^(7′) is an n-valent moiety derived from R⁷ as defined inFormula IIIa and Z is as defined for Formula IIIa; In Formula IIIc; n isan integer greater than 1; R⁷ is as defined in Formula IIIa; and Z′ isan n valent moiety derived from a species selected from the groupconsisting optionally substituted alkyl, optionally substituted aryl anda polymer chain where the connecting moieties are selected from thegroup consisting of aliphatic carbon, aromatic carbon, oxygen and sulfurand wherein the substituents for the substituted moieties referred toabove for R⁷, R^(7′), Z and Z′ are selected from the group consisting ofhydroxy, tertiary amino, halogen, cyano, epoxy, carboxylic acid, alkoxy,alkyl having 1-32 carbon atoms, aryl, alkenyl having 2-32 carbon atoms,alkynyl having from 2-32 carbon atoms, saturated carbocyclic ringshaving 3-14 carbon atoms, unsaturated carbocyclic rings having 4-14carbon atoms, aromatic carbocyclic rings having 6-14 carbon atoms,saturated heterocyclic rings having 3-14 carbon atoms unsaturatedheterocyclic rings having 4-14 carbon atoms and aromatic carbocyclicrings having 4-14 carbon atoms.
 3. The process of claim 2 in which themulti-olefinic polymerizable mononomers consist of compounds of theformula

wherein R⁸ and R⁹ are independently selected from the group consistingof hydrogen, halogen, C₁ to C₆ alkyl, and substituted C₁ to C₆ alkyl; Y¹and Y² are independently selected from the group consisting of NR⁹ and Owhere R⁹ is independently selected from hydrogen and alkyl; and Q isselected from the group consisting of alkylene having 1 to 12 carbonatoms, a carbocyclic group, a heterocyclic group, polyalkylene oxide,polyester, and polyurethane and wherein the groups optionally can besubstituted with one or more substituents selected from the groupconsisting of halo, hydroxy, tertiaryamino, substituted amino, silane,epoxy, acrylate and methacrylate.
 4. The process of claim 3 in which themonomers of the prepolymer consist essentially of alkyl methacrylatehaving 2-8 carbon atoms in the alkyl group, a hydroxyalkyl methacrylatehaving 2-4 carbon atoms in the alkyl group and the thiocarbonylthiochain transfer agent is an aromatic dithiobenzoate and the prepolymer isfurther reacted with an azo catalyst; and wherein the monomers of thecore consist essentially of alkyl (meth)acrylate having 1-4 carbon atomsin the alkyl group, hydroxy alkyl (meth)acrylate having 2-4 carbon atomsin the alkyl group, styrene and allyl (meth)acrylate.
 5. A process forforming a microgel which comprise a core of crosslinked polymer andmultiplicity of substantially linear polymeric arms attached to thecore; wherein the process comprises (a) polymerizing monoethylenicallyunsaturated monomers in the presence of an organic sulfonyl halide, anorganic complexing agent and a transition metal to form a prepolymerterminated with a halogen atom that has a weight average molecularweight of 1,000-25,000; (b) polymerizing said prepolymer withmonoethylenically unsaturated monomers and with 0.5-60 mole percent,based on the total moles of monomer of the core, of multi-olefinicpolymerizable monomers containing two or more carbon to carbon doublebonds which are crosslinked in the core to form the microgel having aweight average molecular weight of 10⁴-10⁸; and wherein themonoethylenically unsaturated monomers of the core and the prepolymerare individually selected from the group consisting of alkenes having1-10 carbon atoms, alkyl (meth)acrylates having 1-12 carbon atoms in thealkyl group, hydroxy alkyl (meth)acrylate, wherein the alkyl groups have1-4 carbons atoms, styrene, alkylstyrene, acrylonitrile, glycidyl(meth)acrylate, isobomyl (meth)acrylate, haloalkyl (meth)acrylates,alkoxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, N-substitutedaminoalkyl(meth)acrylates, N,N-di-substitued aminoalkyl(meth)acrylates,cycloalkyl (meth)acrylates, phenoxy (meth)acrylate, alkylene glycol(meth)acrylate, poly(alkylene glycol) (meth)acrylate, acrylamides,methacrylamides, esters of fumaric acid, esters of maleic acid, maleicacid, maleic acid anhydride, N-vinylcarbazole, N-vinylpyrrolidone,vinylpyridine, benzyl (meth)acrylate, vinyl acetate, vinyl chloride,vinylidene chloride, butadiene, isoprene, chloroprene and any mixturesthereof; and wherein the organic sulfonyl halide has the formula A¹SO₂Xwherein A¹ is an aryl, substituted aryl group, an alkyl group or asubstituted alkyl group, and X is chlorine, bromine or iodine; andwherein the transition metal is selected from the group consisting ofCu[I], Ru[I], Ni[II], Re[II], Pd[II], Cu[0], Ni[0], Fe[0], Pd[0], andRh[II].
 6. The process of claim 5 in which the multi-olefinicpolymerizable mononomers consist of compounds of the formula

wherein R⁸ and R⁹ are independently selected from the group consistingof hydrogen, halogen, C₁ to C₆ alkyl, and substituted C₁ to C₆ alkyl; Y¹and Y² are independently selected from the group consisting of NR⁹ and Owhere R⁹ is independently selected from hydrogen and alkyl; and Q isselected from the group consisting of alkylene having 1 to 12 carbonatoms, a carbocyclic group, a heterocyclic group, polyalkylene oxide,polyester, and polyurethane and wherein the groups optionally can besubstituted with one or more substituents selected from the groupconsisting of halo, hydroxy, tertiary amino, substituted amino, silane,epoxy, acrylate and methacrylate.
 7. The process of claim 6 in which inwhich the monomer of the prepolymer selected from the group consistingof alkyl (meth)acrylate and styrene; the organic sulfonyl halideconsists essentially of an alkoxyarenesulfonyl chloride and the organiccomplexing agent consists essentially of an alkyl 2,2′-bipyridine andthe transition metal is Cu[I]; and wherein the monomers of the coreconsist essentially of alkyl (meth)acrylate having 1-4 carbon atoms inthe alkyl group, hydroxyalkyl (meth)acrylate having 2-4 carbon atoms inthe alkyl group, styrene and allyl (meth)acrylate.
 8. A process forforming a microgel which comprise a core of crosslinked polymer andmultiplicity of substantially linear polymeric arms attached to thecore; wherein the process comprises (a) polymerizing monoethylenicallyunsaturated monomers in the presence of a chain transfer agent to formmacromonomers each having a terminal polymerizable ethylenicallyunsaturated group and the macromonomers having a weight averagemolecular weight of 1,000-25,000; (b) polymerizing the macromonomerswith monoethylenically unsaturated monomers and with 0.5-60 molepercent, based on the total moles of monomer of the core, ofmulti-olefinic crosslinking monomers containing two or more carbon tocarbon double bonds which are crosslinked in the core to form themicrogel having a weight average molecular weight of 10⁴-10⁸; andwherein the monethylencially unsaturated monomers of the core and themacromonomers are individually selected from the group consisting ofalkenes having 1-10 carbon atoms, alkyl (meth)acrylates having 1-12carbon atoms in the alkyl group, hydroxy alkyl (meth)acrylate, whereinthe alkyl groups have 1-4 carbons atoms, styrene, alkylstyrene,acrylonitrile, glycidyl (meth)acrylate, isobomyl (meth)acrylate,alpha-beta ethylenically unsaturated monocarboxylic acids, haloalkyl(meth)acrylates, alkoxyalkyl (meth)acrylates, amino alkyl(meth)acrylates, mono N-substituted aminoalkyl(meth)acrylates, diN-substitued aminoalkyl(meth)acrylates, cycloalkyl (meth)acrylates,phenoxy (meth)acrylate, alkylene glycol (meth)acrylate, poly(alkyleneglycol) (meth)acrylate, acrylamides, methacrylamides, esters of fumaricacid, esters of maleic acid, maleic acid, maleic acid anhydride,N-vinylcarbazole, N-vinylpyrrolidone, vinylpyridine, benzyl(meth)acrylate, vinyl acetate, vinyl chloride, vinylidene chloride,butadiene, isoprene, chloroprene and any mixtures thereof.
 9. Theprocess of claim 8 in which the chain transfer agent is a cobalt chelatecontaining Co⁺² or Co⁺³; and in which the multi-olefinic polymerizablemononomers consist of compounds of the formula

wherein R⁸ and R⁹ are independently selected from the group consistingof hydrogen, halogen, C₁ to C₆ alkyl, and substituted C₁ to C₆ alkyl; Y¹and Y² are independently selected from the group consisting of NR⁹ and Owhere R⁹ is independently selected from hydrogen and alkyl; and Q isselected from the group consisting of alkylene having 1 to 12 carbonatoms, a carbocyclic group, a heterocyclic group, polyalkylene oxide,polyester, and polyurethane and wherein the groups optionally can besubstituted with one or more substituents selected from the groupconsisting of halo, hydroxy, tertiary amino, substituted amino, silane,epoxy, acrylate and methacrylate.
 10. The process of claim 9 in whichthe monomers of the macromonomer consist essentially of alkyl(meth)acrylate having 4-8 carbon atoms in the alkyl group and hydroxyalkyl (meth)acrylate having 2-4 carbon atoms in the alkyl group and thechain transfer agent is a cobalt chelate containing Co⁺² or Co⁺³ and isused in combination with an a azo catalyst; and wherein the coremonomers consist essentially of alkyl (meth)acrylate having 1-4 carbonatoms in the alkyl group, hydroxy alkyl (meth)acrylate having 2-4 carbonatoms in the alkyl group, styrene and allyl (meth)acrylate.